The objectives of this project are 1) to demonstrate a mechanism for triglyceride transport from the interior of chylomicrons and very low density lipoproteins by lateral diffusion of partial glycerides through continuous surface films, and 2) to characterize surface monolayers of plasma lipoproteins, and to identify the determinants of the enzymic and non-enzymic modifications that lipoproteins undergo in the circulation. Specific experiments are 1) to determine the stoichiometry of the surface complex of lipoprotein lipase: apoC-11, to compare the turnover number for triglyceride with the lifetime of the enzyme: activator complex in the surface film, and to identify the factors that effect dissociation of the complex; 2) to demonstrate whether or not partial glycerides diffuse from triglyceride-rich lipoproteins into the surface film; 3) to determine the kinetic rate constants for lipoprotein interaction and lipid transfer with stopped-flow fluorescence techniques using pyrene and specific pyrene-containing lipids incorporated in vitro and in vivo by rabbits; 4) to determine the self-diffusion coefficients for several classes of lipids, in monolayers, in liposomes, and in lipoproteins, and to identify the factors that affect the lateral diffusion of lipids in these experimental systems; 5) to identify the determinants of the interactions and lipid transfer between lipoproteins, single bilayer vesicles and defined surface films, employing pyrene-containing lipids, surface radioactivity, surface fluorescence, fluorescence quenching and photochemically induced covalent bond formation; 6) to demonstrate a mechanism of lipid transfer from triglyceride-rich lipoproteins to cultured cells with specific fluorescent and spin-labeled lipids. These studies should provide experimental support for a new hypothesis of lipid transport and provide new insights into the relationship of lipid accumulation and atherosclerosis.